Cangrelor Ticagrelor Transition Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Cangrelor Ticagrelor Transition Study (NCT01766466), a randomized phase 2 study. The primary outcome is Extent of Preservation of Inhibitory Effect Compared With Effect Observed With Cangrelor Alone (at Timepoint 1, Either at 0.5 Hours or 1.25 Hours) or Ticagrelor Alone (Measured 5.25 Hours After Initiation of Cangrelor on Day 1).

2. Clinical Question

This question is about continuity of an antiplatelet effect during treatment transitions. A transition study can assess whether a measured response changes around the point when one drug is started, stopped, or replaced by another. Here, the endpoint uses platelet reactivity as a laboratory measure rather than a reported clinical event. The record describes measurements on Day 1 at two timepoints after cangrelor infusion began, and it defines reference measurements associated with cangrelor and ticagrelor. However, the record does not report the primary-outcome means, standard deviations, treatment contrasts, or inferential results. The stated objective therefore describes what the study set out to examine, not a result demonstrating whether the objective was met.

3. Trial Design

NCT01766466 is recorded as a Phase 2, randomized, open-label study with a factorial model. Enrollment was 12. The study status is completed. The registry lists coronary artery disease as the condition and names The Medicines Company as sponsor. The study start is recorded as 2013-01 and primary completion as 2013-02.

The interventions listed are cangrelor and ticagrelor. The arm descriptions include cangrelor administered as an intravenous bolus followed by a two-hour infusion, with ticagrelor administered either 0.5 hours or 1.5 hours after cangrelor infusion began in two described sequences. Other descriptions specify oral ticagrelor 90 mg every 12 hours for either 6 doses or 7 doses, followed by another cangrelor administration. Some arm-description text is incomplete in the registry record, so the full details of those sequences cannot be reconstructed from the record.

Randomization indicates that allocation was assigned by chance, while the masking field is none, meaning the study is described as open-label. The model is identified as factorial, but the registry record does not report the factor structure, allocation scheme, or planned comparisons in enough detail to explain how the factorial design was implemented. It also does not report a protocol-based sample-size justification, a detailed statistical analysis plan, or whether interim analyses were planned.

The record lists three outcome measures and zero analyses. The primary outcome is a continuous measure reported in terms of percentage of platelet reactivity, with a mean and standard deviation specified as its summary. Although the study description identifies multiple sequences and timepoints, the posted results do not give numerical primary-outcome results. Consequently, the design features and stated objective can be described, but the treatment effects cannot be evaluated from the reported endpoint data.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: Patients with coronary artery disease who were taking aspirin, but not P2Y12 inhibition were enrolled.

Day 1

Day 5

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Extent of Preservation of Inhibitory Effect Compared With Effect Observed With Cangrelor Alone (at Timepoint 1, Either at 0.5 Hours or 1.25 Hours) or Ticagrelor Alone (Measured 5.25 Hours After Initiation of Cangrelor on Day 1), measured over Day 1 measures taken at 2 timepoints after cangrelor infusion start: 0.5 or 1.5 hrs (Timepoint 1) and 5.25 hrs (TImepoint 2).

The primary endpoint concerns the extent to which the inhibitory effect on platelet aggregation is preserved when treatment transitions between cangrelor and ticagrelor. The registry describes residual platelet reactivity as the extent of aggregation in the presence or absence of the study drugs. It was measured using light transmittance aggregometry in response to 20 µmol adenosine diphosphate (ADP), with the terminal aggregation response recorded at 300 seconds.

Measurements were scheduled on Day 1 at two timepoints after cangrelor infusion started: Timepoint 1, identified in the timeframe as 0.5 or 1.5 hours, and Timepoint 2 at 5.25 hours. The endpoint title separately refers to Timepoint 1 as either 0.5 hours or 1.25 hours. This difference in the stated Timepoint 1 timing is present in the registry record and cannot be resolved from the available description. The record designates an early draw during cangrelor infusion as the reference for cangrelor’s effect and the final Day 1 draw as the reference for ticagrelor’s effect.

As a general statistical interpretation, platelet reactivity provides a laboratory measure of the biological response under study; it is not itself a clinical event. Comparing measurements at defined treatment times can describe whether the measured response is maintained across a transition. The registry specifies a mean and standard deviation as the endpoint summary, but it does not report the numerical measurements or a treatment contrast. Therefore, the endpoint’s intended role is clear, while its observed results and precision are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous and is specified as a mean with a standard deviation. As a general statistical explanation, a mean describes the central value of a set of measurements, while a standard deviation describes how spread out measurements are around that mean. Both can help characterize a group’s observed platelet reactivity. The registry record does not report the actual means or standard deviations for the primary outcome, so these summaries cannot be interpreted for this study.

In a transition study, the central statistical question may concern changes in a measurement across treatment conditions or timepoints. A difference in means can describe the size and direction of a contrast. A confidence interval, when reported, describes uncertainty around an estimated quantity under the assumptions of the analysis. A p-value can summarize how compatible the data are with a specified statistical null model; it does not measure the probability that a treatment effect is true. These are general explanations. The registry record does not report a primary-outcome contrast, confidence interval, or p-value, and it does not report the null hypothesis or test used.

The endpoint uses light transmittance aggregometry in response to 20 µmol ADP and records the terminal aggregation response at 300 seconds. These procedural details define how the laboratory response was measured. The record describes an early reference draw during cangrelor infusion and a later Day 1 reference draw associated with ticagrelor. Repeated measurements can be useful for describing change over time, but their analysis needs to account appropriately for the fact that measurements from the same participant are related. The statistical model used for such measurements is not reported in the registry record.

The trial is described as randomized, open-label, and factorial. Randomization can reduce systematic differences between allocated groups on average, while open-label status means masking is not recorded. A factorial design generally examines combinations of factors or treatment conditions, but its interpretation depends on the factors, allocation, and planned contrasts. Those details are not reported sufficiently to infer the intended factorial comparisons. The registry record also does not specify whether the reported endpoint analysis, if any, adjusted for baseline values or other covariates.

The registry record lists three outcome measures and zero analyses. This means the posted record does not include analysis entries from which the primary endpoint estimate or its uncertainty can be recovered. The record does not state the analysis population, the handling of missing endpoint measurements, the treatment of protocol deviations, or whether results were analyzed according to randomized allocation. These are important features because different choices can affect estimates and their interpretation. Their absence should not be filled by assuming a conventional approach.

For planning illustrations, the record describes calculations based on an observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says that the effect to detect is a stated fraction of the observed effect, and that non-time-to-event illustrations are expressed as participants per arm. These are planning assumptions, not observed trial results or observed power. The numerical illustrations and the specific fractions are not reported in the registry record. They should not be interpreted as the trial’s original sample-size justification, which is also not reported.

As a general concept, over-dispersion occurs when observed variation exceeds what a chosen statistical model assumes. If present, it can make standard errors too small and confidence intervals too narrow unless the analysis accounts for the extra variability. The record does not report a model or diagnostic assessment that would show whether over-dispersion was relevant to this endpoint. More broadly, the absence of outcome estimates and analysis details means that the statistical evidence cannot be independently assessed from the registry record, even though the measurement and summary type are described.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists three outcome measures, but it does not report a multiplicity strategy. When a study evaluates several outcomes, timepoints, treatment contrasts, or subgroups, testing many hypotheses can increase the chance of a false-positive finding across the set of tests. As a general statistical principle, multiplicity procedures can control or describe that risk, but the appropriate approach depends on which comparisons were planned and which were considered primary. The record does not identify such a procedure or a hierarchy of hypotheses.

The primary endpoint refers to more than one measurement time and to reference measurements associated with cangrelor and ticagrelor. The record does not explain how those measurements were combined into a primary contrast, whether each timepoint was tested separately, or how any resulting tests were handled. It also lists zero analyses, so no multiplicity-adjusted or unadjusted results are posted.

Missing-data methods are not reported in the registry record. There is no description of the number of missing primary endpoint measurements, how missing observations were handled, or whether participants with incomplete data were included in an analysis. The analysis population is also not reported. The registry record does not say whether the primary analysis included all randomized participants, only participants with available measurements, or another defined group.

These omissions matter because decisions about endpoints, timepoints, missing observations, and analysis populations can change the interpretation of a result. They do not establish that a particular method was or was not used; they mean that it is not reported in the registry record. With no numerical endpoint analyses posted, readers cannot evaluate the effects of those choices on the findings.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists two safety groups: Cangrelor + Ticagrelor 90mg (6 Doses) and Cangrelor + Ticagrelor 90mg (7 Doses). Each group lists 6 participants at risk for serious adverse events and 0 participants affected by a serious adverse event. Each group also lists 6 participants at risk for other adverse events and 1 participant affected by an other adverse event. These are counts as recorded; no percentages or further event details are reported.

The serious adverse event counts are distinct from the other adverse event counts. The one participant with an other adverse event in each group should not be described as having a serious adverse event on the basis of these entries. The registry record does not list serious adverse event terms in its top-term information. Death counts are not reported in the registry record.

As a general statistical point, safety counts describe events recorded in the listed groups; they do not by themselves establish whether an event was caused by a treatment. With 6 participants at risk in each group, the counts are limited observations, and the record does not provide additional information about event type, timing, severity beyond the serious/non-serious classification, or attribution. The entries should therefore be read as descriptive registry counts, not as a comparative estimate of safety or evidence about risks beyond the participants and events recorded.

12. What the Result Does, and Does Not, Mean

The registry record documents a randomized study of transitions between cangrelor and ticagrelor and describes a laboratory endpoint intended to assess preservation of platelet inhibition. It also records enrollment of 12 participants and gives limited adverse-event counts for two groups. These registry entries describe the study and some posted safety information; they do not provide the primary endpoint result.

No numerical primary outcome estimates, contrasts, confidence intervals, or p-values are reported. The study objective cannot therefore be treated as an established result. In particular, the record does not show whether platelet reactivity changed during a transition, how large any change was, or how uncertain an estimate would be. It does not support a conclusion that the measured inhibitory effect was preserved or reduced.

The endpoint is a laboratory measure and should be interpreted as such. The record does not report clinical outcomes or establish whether the laboratory measurements corresponded to changes in clinical events. The safety counts are also descriptive and sparse: each listed group has 0 participants affected by a serious adverse event and 1 participant affected by an other adverse event, among 6 at risk. These counts alone do not establish comparative safety or causation.

The factorial design label and randomized allocation are relevant design descriptors, but the record does not provide the full allocation structure or statistical comparisons. The ambiguity in the stated Timepoint 1 timing is another reason to avoid inferring more than the record says. Overall, the posted information describes the question, measurement approach, and limited safety counts, but it does not permit an assessment of the primary treatment effect or its precision.

13. Why This Trial Matters Statistically

This study raises a statistical question about how to evaluate a treatment transition using a repeated laboratory measurement. The endpoint is defined around residual platelet reactivity, with measurements linked to different points in the cangrelor and ticagrelor sequences. Such a design makes clear why timing, reference measurements, and the planned comparison need to be specified: the meaning of a measured change depends on which observations are being contrasted.

The registry record also illustrates the distinction between a study objective and an analysis result. The aim refers to avoiding a significant decrease in platelet inhibition, but the record lists zero analyses and does not post numerical primary endpoint results. Without estimates and uncertainty, a reader cannot determine whether the data support the stated objective. A design description, even with a defined assay and timepoints, is not a substitute for reporting the results of the planned comparison.

The small enrollment and the safety group counts further emphasize the importance of precision and transparent reporting. The record does not include the primary endpoint variability or a confidence interval that would show how much uncertainty remains. It also does not explain the factorial comparisons, multiplicity approach, missing-data handling, or analysis population. Those are not merely technical details: they are needed to understand what estimate is being made and to judge its reliability.

Statistically, the study matters as an example of a transition question in which the choice and timing of a laboratory endpoint are central, while the available registry record leaves the main inferential result unreported. The proper conclusion is not about whether either drug sequence achieves the objective, but about the limits of what can be learned from the posted data.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The most important limitation for interpreting this trial is that numerical results for the primary endpoint are not reported in the registry record. Although the endpoint is defined and the measurement method is described, the record does not give its observed means, standard deviations, contrasts, or uncertainty estimates. It therefore does not allow readers to assess the primary treatment question.

Enrollment was 12, and the registry lists 6 participants at risk in each of the two safety groups. The record does not provide primary-outcome denominators or explain whether all randomized participants contributed measurements. The analysis population, missing-data handling, and any exclusions are not reported in the registry record.

The primary endpoint description contains a timing inconsistency: Timepoint 1 is described as 0.5 or 1.25 hours in the endpoint title, but as 0.5 or 1.5 hours in the timeframe. The record does not clarify which timing is correct. Some arm descriptions are also incomplete, so all treatment-sequence details cannot be established. Although the design is called factorial, the factors and planned contrasts are not sufficiently described to interpret the intended comparisons.

The record lists three outcome measures but does not report a multiplicity plan, statistical model, or analysis results. It also does not report the trial’s sample-size justification or whether interim analyses were planned. These limitations mean that the study objective and measurement approach can be described, but the strength, precision, and robustness of the primary evidence cannot be evaluated from the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Cangrelor Ticagrelor Transition Study — NCT01766466.
• Registry record last updated 2014-05-19; status last verified 2014-04.
• Results first posted 2014-05-19.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT01766466 is titled “Cangrelor Ticagrelor Transition Study,” with the official title “A Study of the Transition From Cangrelor to Ticagrelor, and Ticagrelor to Cangrelor in Patients With Coronary Artery Disease.” The sponsor is The Medicines Company. The condition is coronary artery disease, and the listed interventions are cangrelor and ticagrelor.

The study is recorded as Phase 2, randomized, open-label, and factorial. Enrollment was 12. The study start is 2013-01, primary completion is 2013-02, and status is completed. Three outcome measures are listed, with zero analyses recorded.

The primary endpoint concerns preservation of inhibitory effect as assessed through residual platelet reactivity measured by light transmittance aggregometry. Numerical primary-outcome results are not reported in the registry record. Safety entries list 0 serious adverse events among 6 participants at risk in each of two groups, and 1 other adverse event among 6 participants at risk in each group.